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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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    <script>
        let age = prompt('请输入年龄');
        let futureAge = +age + 5;
        alert('我估计，五年后，你的年龄是：' + futureAge + '岁')
    </script>
</body>

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